Objectives. A quick cold start of emergency and auxiliary power units based on diesel engines should be possible at any time without problems and in the shortest possible time. The condition of the engine oil is one of the most important factors influencing the smooth start-up of power plants. During diesel engine operation, engine oil accumulates soot in its composition, negatively affecting its rheological properties. The aim of this research is to develop a mathematical model to describe changes in the dynamic viscosity of motor oils as a function of temperature. This model will account for the concentration of soot and its morphology, based on the results of experimental studies.
Methods. Standardly used motor oils for diesel engines M-14D₂SE and M-5z/14D₂SE were used as oil samples in the preparation of model mixtures. The dispersed phase of the suspensions comprised carbon black of the N110, N220, N330, and N220 grades, characterized by a dusty (nongranular) texture. The rheological properties of the samples were determined using a TA Instruments DHR-2 rotational rheometer. The experimental data was subjected to mathematical statistical processing, in order to obtain approximating dependencies.
Results. The paper presents an analysis of the various approaches to the description of the rheology of suspensions and the results of experimental studies of the viscosity-temperature characteristics (VTCs) of model samples of oils containing soot. The extant models of the dependence of the dynamic viscosity of suspensions on temperature, volume concentration of the dispersed phase, particle size and shape are demonstrated to be inadequate for the description of the VTCs of motor oils containing soot. A model of the rheological properties of soot-oil suspensions is proposed in the form of a mathematical dependence of their dynamic viscosity on temperature, mass concentration of soot, material density and size of soot particles, characteristics of the shape and structure of primary aggregates and the ratio of the sizes of aggregates and molecules of the dispersion medium.
Conclusions. It was demonstrated that a comprehensive description of the VTCs of engine oils containing soot necessitates the consideration of the structural characteristics of the primary aggregates of soot particles. A mathematical model of the VTCs of oils was developed. This model is based on the dependence of the dynamic viscosity of oils on temperature, mass concentration of soot, density of the particle material, degree of non-sphericity of aggregates, the ratio of the particle sizes of the dispersed phase (either aggregates orsingle particles of non-aggregated soot) and oil molecules, and on the structure ofsoot, characterized by adsorption of dibutyl phthalate.

 Objectives. To develop a highly efficient catalytic system for the liquid-phase oxidation of long-chain mono-chlorinated alkanes by oxygen in air to a mixture of high-boiling chlorinated carboxylic acids, which can serve as raw materials for the production of multifunctional additives for polyvinyl chloride.
Methods. The liquid-phase oxidation of 1-chloro-n-hexadecane by oxygen in air in the presence of a two-component catalytic system of St₂Co(OH) and N-hydroxyphthalimide (N-HPI) was investigated. The air flow rate during the oxidation of 1-chloro-n-hexadecane was controlled by a gas meter. Identification, composition, and content of the starting 1-chloro-n-hexadecane for conversion control were conducted using chromatographic-mass spectrometric analysis on an Agilent GC 7820A/MSD 5975 instrument. The structure of cobalt(III) hydroxystearate was confirmed by infrared spectroscopy.
Results. Investigation of a two-component catalytic system St₂Co(OH)–N-HPI in the oxidation reaction of 1-chloro-n-hexadecane by oxygen in air revealed that both components of the system participate in the formation of hydroperoxides. This accelerates their formation and contributes to high hydroperoxide content in the reaction mass. It was observed that St₂Co(OH) in the two-component catalytic system accelerates the decomposition of hydroperoxides better than St₂Co in another two-component catalytic system previously studied, making it promising for application in the process. The oxides thus obtained can serve as raw materials for the production of multifunctional additives for polyvinyl chloride which could lead to improvements in the quality and properties of this material.
Conclusions. The investigation into the liquid-phase oxidation of 1-chloro-n-hexadecane by oxygen in air using the two-component catalytic system St₂Co(OH)–N-HPI has shown it to be more efficient compared to the two-component catalytic system St₂Co–N-HPI. The optimal concentration of the two-component catalytic system St₂Co(OH)–N-HPI in the reaction system for the liquid-phase oxidation of 1-chloro-n-hexadecane by oxygen in air has been determined to be 9 mol % of the raw material loading, with a molar ratio of components of 1 : 6. Such a catalytic system enables an acid number in the oxide of 42 mg KOH/g to be attained after 10 h of oxidation.

Objectives. The work set out to develop a bioreactor that incorporates a carbon dioxide removal unit within the apparatus gas phase, which is capable of operating without the need for supplementary compression apparatus. As part of testing the developed equipment in order to ascertain its capacity for enhanced biomass production, the principal fermentation system parameters that facilitate the optimal bioreactor productivity in conditions of carbon dioxide removal from the apparatus gas phase were identified.
Methods. A series of tests were conducted on the fermentation unit with the objective of controlling the oxygen and carbon dioxide content in the gas phase of the bioreactor. This was achieved using an in-line gas analyzer fitted with electrochemical sensors. The oxygen and carbon dioxide content in the gas phase was determined by means of gas chromatography. The oxygen and natural gas flow rates were determined using a thermal electronic flow controller equipped with thermoresistive elements. The oxygen content of the cultural liquid was determined by means of an optical oxygen sensor with integrated transducer. The pH level in the bioreactor was monitored and maintained using an electrochemical pH sensor.
Results. The efficacy of the newly devised jet-type bioreactor design, which permits the incorporation of a carbon dioxide removal unit into the fermentation system without requiring supplementary compression apparatus, was evaluated through experimentation. The system was tested with the carbon dioxide removal unit included in the design, resulting in a 64% increase in bioreactor productivity and a 18% reduction in oxygen consumption as a component of the gas supply.
Conclusions. The operational parameters of a technological bioreactor that facilitate a stable continuous process of bacterial cultivation were identified.

Objectives. To investigate polymer composite materials based on poly-3-hydroxybutyrate (PHB) of microbiological origin and the synthetic nitrile butadiene rubber NBR-28. The biodegradability of PHB implies the possibility of its use for invasive medical purposes; however, this is significantly limited by its brittleness. The aim of this work was to search for approaches to altering the molecular structure of PHB-based composites, in order to impart them with sufficient physical and mechanical characteristics and increase their compatibility without violating biodegradability.
Methods. Reaction mixtures contained the elastic material NBR-28, various modifiers (sorbitan oleate, epoxidized soybean oil, siloxane rubber), and additional polymer components (ethylene–vinyl acetate copolymer and polybutylene adipate terephthalate). The mixtures were prepared in a PL 2200-3 plasticorder (Brabender, Russia) by pressing, holding the material at 180°C under pressure for 3 min followed by quenching in cold water. The surfaces of the films and plates of the mixtures were studied using an Axio Imager Z2m optical microscope (Carl Zeiss, Germany) with the Axio Vision software at 50× and 200× magnification in reflected light. The mechanical properties of materials under tension were measured using an Instron 3365 universal tensile testing machine (Instron, United Kingdom).
Results. The role of modifiers and polymer additives in the PHB–NBR-28 composites and their influence on the morphology of mixtures, crystallinity, and mechanical characteristics were established. The introduction of modifiers made it possible to reduce the average particle size of the NBR-28 phase in the PHB matrix by 30–50%, additionally changing their morphology. In this case, the uniformity of particle distribution increased, having a positive effect on the mechanical characteristics of the systems.
Conclusions. It was shown that the modifiers change the morphology of mixtures, reduce the average particle size of the NBR phase by 30–50%, and positively affect the strength of the systems. Owing to changes in the structure of their interfacial layers and, as a consequence, physical and mechanical characteristics, the resulting composites render suitable for use in reparative bone and dental surgery, as well as for creating wound healing materials.

Objectives. The aim of this study is to ascertain the influence of polyetherimide on the curing process of epoxy binders.
Methods. The storage modulus and loss modulus of epoxyamine systems were measured as a function of curing time on the Anton Paar MCR 302 rheometer. The experiments were carried out at an oscillation frequency of 1 Hz, with an amplitude aligned with the linear viscoelasticity region, and across a range of temperatures (160, 170, and 180°C). The crossover point was determined when the components of the complex modulus of elasticity are equal according to the obtained dependencies.
Results. The influence of polyetherimide on the curing process of epoxyamine binders was investigated at a thermoplastic content of 5 to 20 pts. wt at three temperatures. In a system modified with 20 pts. wt of polyetherimide, phase separation was observed during the curing process. In systems modified with 10 and 20 pts. wt of polyetherimide, the limiting value of the modulus of elasticity was observed to be higher at 170°C than at 180°C.
Conclusions. The modification of epoxyamine binders with thermoplastic in an amount of 5–20 pts. wt has been observed to extend the time required to reach the crossover point. Furthermore, the curing process markedly slows down in the system comprising 10 pts. wt of thermoplastic content, in which it takes the longest time to reach the crossover point at all three experimental temperatures.

Objectives. The study set out to examine the impact of pre-mixed ultra-high molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) on a range of properties and structural characteristics of SKEPT-50 ethylene propylene diene monomer (EPDM) rubber.
Methods. The production of rubber mixtures involved the pre-mixing of rubber with UHMWPE and HDPE in a Brabender PL 2200-3 plasti-corder chamber (Germany) at a temperature of 160°C, for a period of 6 min, and with a rotor speed of 60 rpm. The polyethylene constituents were incorporated into the rubber compound at concentrations of 5, 10, and 15 pts. wt. The subsequent introduction of the principal constituents of the rubber mixture was conducted in an SYM laboratory mill (China) for a period of 30 min at a temperature of no more than 100°C. The vulcanization of the samples was conducted in an Y1000D vacuum hydraulic press (China) at a temperature of 185°C for a period of 35 min. The investigation of vulcanization and physical and mechanical properties was conducted in accordance with the established protocols. The analysis of the rubber supramolecular structure was conducted using a JEOL JSM-6840 LV scanning electron microscope (Japan).
Results. The results demonstrate that an increase in the proportion of HDPE and UHMWPE to 15 pts. wt leads to a notable enhancement in the hardness of the rubbers by 10 and 5 Shore A units, respectively. The frost resistance coefficient at −45°C demonstrates an increase with the incorporation of 10 pts. wt of HDPE to reach a value of 0.229, and a further increase with the incorporation of 15 pts. wt of UHMWPE to reach a value of 0.260. The degree of swelling of rubbers in a DOT-4 brake fluid environment is observed to decrease to 13% for rubbers with HDPE and 19% with UHMWPE. The degree of swelling of rubbers in the DOT-4 brake fluid environment is observed to decrease to 13% for rubbers with HDPE and 19% with UHMWPE. While an increase in the HDPE content results in a 5% increase in volumetric wear, an increase in the UHMWPE content is associated with a 45% decrease in volumetric wear. The introduction of UHMWPE was observed to result in the formation of inclusions of varying shapes and sizes within a range of 50–100 µm. The transition zone between UHMWPE and rubber is characterized by a smooth surface. No evidence of cracks or micro-tears between the polymer phases, which could potentially form during low-temperature splitting, was observed. This finding indicates the presence of favorable interfacial interactions, which can be linked to the observed enhancements in resistance to aggressive liquids and abrasion, as well as the improved tensile frost resistance coefficient. The supramolecular structure of rubber samples combined with HDPE is more pronounced and exhibits greater relief than that of the original rubber. This is indicative of a more uniform distribution within the matrix volume, which can be attributed to the high fluidity of the HDPE melt.
Conclusions. Rubbers modified with UHMWPE, in comparison with HDPE, exhibit enhanced resistance to wear, oil, and frost, while maintaining their elastic and strength properties. It was established that rubber containing 15 pts. wt of UHMWPE exhibits optimal properties and can thus be recommended for use in sealing rubber products.

Objectives. To obtain highly dispersed powders of chromium(III) molybdate Cr₂(MoO₄)₃ by solid phase synthesis and to study their porous structure.
Methods. After stirring in water, a mixture of Cr₂O₃ and MoO₃ oxide powders was dried in air and subjected to heat treatment in the temperature range of 600–800°C. After heat treatment, the products were identified by X-ray phase and sedimentation analysis. The specific surface area was measured using the Brunauer–Emmett–Teller static adsorption method. Porosity parameters were measured using the Barrett–Joyner–Halenda (BJH) method.
Results. The Gibbs free energy ΔG of the reaction between chromium and molybdenum oxides was calculated and it was shown that the process is characterized by a significant negative value of ΔG. Concurrently, the Gibbs energy exhibits a relatively weak dependence on temperature. The highly dispersed chromium(III) molybdate powders with specific surface area of 15.3–29.7 m²·g⁻¹ obtained in this way were pure according to X-ray diffraction analysis. A study of the volume, diameter, and pore size distribution was conducted through the utilization of nitrogen adsorption–desorption isotherms in accordance with the BJH model.
Conclusions. It was demonstrated that Cr₂(MoO₄)₃ powders possess a mesoporous structure and are distinguished by a bimodal pore system comprising small pores with a diameter of 2–3 nm and larger pores with a diameter ranging from 15 to 30 nm.

Objectives. To develop mathematical approaches and algorithms for analyzing the influence of various methods for feeding a chain transfer agent to a cascade of reactors, taking into account the choice of feed points on the characteristics of the final product of copolymerization using computer modeling.
Methods. The processes of synthesis of copolymers were mathematically modeled using a statistical approach (Monte Carlo method). The developed algorithm is based on calculating the probabilities of elementary reactions in the process under study. In the case of continuous production of the copolymer in a cascade of reactors, it must be taken into account that the residence time of each particle of the reaction mixture in the reactor is subject to a probability distribution. The algorithm models the formation of copolymer macromolecules at the particle level, permitting the average molecular characteristics of the copolymer to be calculated and its microstructure to be studied based on modeling results.
Results. The dependencies of the intrinsic viscosity on the reactor number and conversion were constructed by means of mathematical modeling. The calculation results showed satisfactory agreement with the experimental data obtained in production. The dependencies of the molecular weight distribution of the copolymer, the weight-average molecular weight, and the microheterogeneity index on the reactor number were constructed for various methods of feed of the chain transfer agent, i.e., to two and/or three points of the reactor cascade. The modeling and calculation results confirmed the influence of the method of adding the chain transfer agent to the cascade reactors on the molecular characteristics of the copolymer.
Conclusions. The analysis of the structure of the molecular units of the styrene–butadiene copolymer showed a decrease in the weightaverage molecular weight of the final product and an increase in its stiffness in the case of the three-point feed of the chain transfer agent.